Preparation of pentaerythritol



.PatentecLJuiy 2, 1940 rmmrronor'rmmrrnauor.

Jolop h A. wyler, Allentown, Pq minor-to Troianlowder-Onmpany, Allentown, Pa. I

. a No me... Application April 27,1930.

' Serial no. 210,340

4 omm. (d1. zoo-cs5) This invention relaterto a processjior the preparation ofpen'taerythrltol and more particularly to a process for the alkalinecondensation of. formaldehyde and acetaldehyde to pentaerythritolthrough the use of a combination of catalysts.

In my co-pending application 8. N. 200,683 is disclosed the process for the preparation of pen- 1 taerythritol from formaldehyde 'and acetaldeo hyde through the use of oxalates oi! metals oi the 1st long period of Mendelejefl's Periodic System having atomic weightsbetween 52 and 63.6.

I have now discovered that if certain agents be I used in combination with the above mentioned catalysts .that further important improvements in the process result.

It is well known that pentaerythritolis formed by the condensation of tour molecules of formaldehyde with one molecule of acetaldehyde in the presence of such alkalies as NaOH, KOH, Ca(H)z. or Ba(0H)z, and although; many such processes are described in the literature, the yields are usually low-approximately 60% of theory. In addition to the low yields, further un- 2 favorable factors in these processes are the formation of a relatively large amount of a, dark colored, resinous syrup and the length of time required to complete the reaction.

It is an object of my invention to increase the yield of pentaerythritol received from a given amount of aldehydes. A further object is to prevent the formation of. colored products during the condensation of the (31120 and CHaCHO. A still further object is to shorten the time required to complete this condensation. Other and further objects will become apparent upon a perusal of this specification.

In general, the commercial condensation of CHzO and CHaCI-IO is based upon the use of 4 to 5 molecules of formaldehyde for each molecule of acetaldehyde in alkaline media, at temperatures not exceeding C., and in such a-volume of water as to provide a solution to contain less than 20% of aldehydes at the beginning of the reaction.

Although the general reaction for the formation of pentaerythritol is as follows: I

the pentaerythritol is generally believed to be the result of the following reactions:

.In addition to these reactions others, producoo ing sugary, syrupy products also take place and it is evident that the more perfect the balance between reactions 1 and 2, thegreater theyield.

o1'.1i entaerytluitol and the less the yield 01 syrupy products.

Intheabove mentioned application Ihave disclosed the use oi oxalates oiFe, Co, Cr, Mn, Ni, and Cuindividually or in admixture, as agents for effecting a more complete balancing of the above reactions and in the'present application I am disclosing the use of C1120, Cu or Pt or mixtures of these in combination with any of the above oxalates or mixtures thereof.

'Cu2O, Cu or Pt has the effect of causinga more thorough hydrogenation of MacLeods aldehyde and it also shortens the time required to do this, other conditions being uniform. I

The following examples in which all parts given are by weight, illustrate-my invention.

Example #1 396 parts of 30.34% formaldehyde and 79.5"" parts of 52.8% commercial acetaldehyde are mixed with 966 partsof water in a suitable container provided with astirrer. To this is slowly 30 added, with stirring, a mixture of 40 parts of CaO and 100parts oi'water. This slurry is added over a period of three to five hours and the reaction mixture is kept at approximately 20 to 30 C. throughout the period of addition- 35 Just before the beginning of the addition of the lime slurry, 0.25 part of finely powdered copper oxalate is added to the mixture of aldehydes, and when about half the lime is in, 1 part of 01120 is added. After all the lime is-in, the o stirring is continued, at "20 to 30 C., until an iodine titration indicates less than, say, 0.10% of total aldehydes, calculated to CHaO. The time to arrive at this point varies somewhat but it is usually not over 6% to '7 hours. 5

The reaction mixture, at completion, is treated with slightly less sulphuric'acid than is theoretically equivalent to the lime used. This precipitates most of the lime as calcium sulfate. In order to precipitate all of the calcium out of 50 solution, a small amountof oxalic acid is added in the form or a water solution and the mixture stirred for an hour or more, when it is filtered. The filtrate is evaporated and the pentaerythritol recovered by crystallization.

I1 this same run had been made without the addition of the C1120 the time required i'or the reaction would have been about 20 hours and the yield of pentaerythritol about of theory. (Based on either the acetaldehyde or on the o0 yields I of ,"penta'erythritol, any ldipentaerythritol which-iorms is considered- 'a's pentaerythritoL. I

I r .1 a ioilireshlyreduced Cuisuaed in'thec ondensation' reaction mixture in place or the C1120 mentioned in' Example ;#1, and the process carried out' essentially asthere described.

simple-# I 0.03pm freshly? prepareQpIatinum blac is. used in the condensation reactionmixture in place oi the CuzQ'mentionedinExampi'e #1, ex;-

cept that-inthis ease-.21. preier-to add the mat inurn somewhat later inithe condensation process, thatisgat the stage-wherethe'acetaldehyde has' practically. all been converteditorMacLeods aldehyde, "'fIhisjis indicated ,wheniabbut 75%01' the totaloriginal-aldehydic contentjms indicated by rythritel?of over 90% 9f thecry are'obtainable.

- In 'th'ese exafrnplesonly thepreierred conditions are given.- Tmaysta'rt cut withstronger ccncentrations f, aldehydefss se :a lesser or greater amountofthe metal oxalate, cuprous oxide, coppero'r-platinumii use'uiny water soluble fixed alkali as Ba(OH) a, SflOHXzZ'NaQH, xomkicos, NazCQ a; (CHi) 4N(O H) (CzxHt) 4N( OH) etc.; vary the temperature at which the reaction'is' carried a workman skilled in this art; without departing out, the. rate of additionofthealkali or, the amount of alkali; or, in short,I may 'use such operative, conditions or details as would occur to from the essenceoi this invention.

I Claim:

1. The procession the preparation of pentae- 1- r a. r i 2,2 7

""iormaldehyde.) the present example we yield is 90.%'tQ 92 0! theory. 1 In calculating therythritol comprising the condensation in aqueous media oi. formaldehyde and acetaldehyde to pentaerythritol in the, presence of a'fixed alkali, an oxalate .of a metal of the 1st longperiod of Mend'elejeifi's Periodic 'System, having an atomic weight between 52 and 63.6, and a member of the group consisting of finely divided cuprous oxide and copper.

'2. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetaldehyde to pentaerythritol in the presence of a fixed alkali, an oxalate of a metal of the lstlong period of Mendelejefl's Periodic System, having an atomic weight between 52 and 63.6, and a member of the group consisting of finely divided cuprous oxide and copper, the molecular ratio of the formaldehyde to acetaldehyde being approximately four to'oneand the total aldehyde content of the solution being less than 20% by weight.

- 3. The-process forthe preparation of pentae- 'rythritol comprising the condensation in aqueous j media of formaldehyde andacet'aldehyde to pentaerythritol in thepresence of calcium hydroxide,

copper oxalate and a member of the group con- ,sistingjof finely divided cuprous oxide and copper, molecular ratio of the formaldehyde to the acet'aldehyde being approximately four to one and less than by weight.

4. The process for the preparation of pentaerythritol comprising the condensation in aqueous media oi-iormaldeliyde and acetaldehyde to penthe total aldehyde content 01 the solution being taerythritol-in the presence of calciumhydroxide,

copper oxalate and 'a member or the group con- :sisting offinely divided cuprous-ioxide and copper,

the molecular ratio-of the formaldehyde to the 'acetaldehyde being approximately four to one,

and the total aldehyde content of the solution being less, than 20% by weight, the proportion, by

weight, of the copper oxalate to "formaldehyde (100%) being approximately 0.25 to 119, that of the cuprous oxide being about one-to 119, that 01' the copper being about one to 119.

I JOSEPH A. WYLER. 

